556 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1910. 



breeding grounds in Alaska. So protracted is the molt of the species 

 that it is probably true that during the stay of this plover in Ha- 

 waii — from middle August till May — there is not a month when some 

 individuals are not molting. 



There is no reason for believing that the plover summering in the 

 islands, which, as before stated, are chiefly if not wholly immature 

 birds, participate in the spring molt. At all events, all the Hawaiian 

 summer plover and turnstones I have seen were, without exception, 

 in the winter garb. 



Why the plover migrates. — ^We have thus seen that what at first 

 might appear a physical impossibility — the 2,000-mile flight of small 

 birds across an ocean highway without a single landmark and with 

 only the friendly winds to guide them, if indeed they utilize these as 

 guides — is not only possible, but the feat is accomplished annually by 

 many thousands of individuals, and apparently with no stops for rest 

 and food. The wonder of it is but increased when we realize that 

 these annual flights are undertaken solely for the purpose of making 

 a sojourn of a few brief weeks in Alaska to nest and rear their 

 young. The hazards of such journeys are very great — much greater 

 than any land migration, however prolonged — and there is no doubt 

 that of the thousands daring the perils of the trip from Alaska many 

 are lost, either by missing the islands altogether or by being caught 

 in storms, or by reason of insufficient strength and wing power. The 

 flight from the islands to Alaska, though not without danger, is less 

 hazardous than the southern flight, both because a much greater pro- 

 portion of the migrants are mature and experienced and because, in 

 case they lose their way, they have two continents as marks to hit. 



The motive for the fall migration of the plover, like that of the 

 other waders breeding in the far North, is easily understood. What- 

 ever may have been the case in the distant past, to-day the waders 

 have no alternative. They must migrate from the Arctic in the fall 

 or starve. The only choice offered is as to the selection of winter 

 quarters. Thus compelled to migrate, it appears that a certain num- 

 ber of plover and of several other shore-birds find the Hawaiian 

 Islands a winter resort so attractive that to reach them they brave 

 the perils of migration across a wide and stormy ocean. Why, then, 

 do they not permanently colonize the islands? If adajoted to the 

 bird's needs for nine months of the year, why not for the other three? 



It can not be said of the spring migration of these Hawaiian 

 migrants as of the fall, that the birds have no alternative. On the 

 contrary the choice is open, and they would seem to have every incen- 

 tive to remain, with no very apparent motive to migrate. The chief 

 cause compelling winter visitors to the Tropics to leave and to seek 

 northern regions in which to breed has been supposed to be the over- 

 crowding of the Tropics in spring and the resulting lack of room and 



